Nuclear spin-induced Cotton-Mouton effect in molecules

Area of Science:

• Nuclear magneto-optic spectroscopy
• Quantum chemistry
• Molecular physics

Background:

• Nuclear magnetization influences light polarization.
• Nuclear spin optical rotation is an optical analogue of NMR chemical shift.
• The nuclear spin-induced Cotton-Mouton (NSCM) effect is a magneto-optic analogue of NMR spin-spin coupling.

Purpose of the Study:

• To formulate the nuclear spin-induced Cotton-Mouton (NSCM) effect using first-principles electronic structure.
• To investigate the roles of basis set, electron correlation, and relativistic effects on NSCM.
• To explore NSCM as a tool for determining molecular structure and dipolar coupling.

Main Methods:

• First-principles electronic structure formulation using response theory.
• Ab initio and density-functional theory calculations for small molecules.
• Analysis of temperature-dependent contributions and tensor properties.

Main Results:

• A theoretical framework for NSCM was established.
• The temperature-dependent contribution, driven by molecular orientation, typically dominates NSCM.
• NSCM is proportional to the tensor product of molecular polarizability and NMR direct dipolar coupling.
• Predicted ellipticities are on the order of 10⁻⁸–10⁻⁷ rad/(M cm) for fully polarized nuclei.

Conclusions:

• NSCM provides a novel method for investigating dipolar coupling and molecular structure in isotropic media.
• The predicted NSCM magnitudes are experimentally detectable with current instrumentation in the Voigt setup.
• This work establishes a foundation for utilizing nuclear spin effects in optical spectroscopy for structural analysis.